1. Field of Invention
Exemplary aspects of the present invention relate to an image forming apparatus, and more particularly to an image forming apparatus employing a development unit including a developer carrying member and developer conveyance mechanisms.
2. Description of the Related Art
In general, an image forming apparatus of recent years has been demanded to enhance stability of an image quality without having density unevenness, etc. when images with high image area ratios are successively printed one after another.
A related art image forming apparatus has shifted configuration thereof by disposing a developer conveyance mechanism in a longitudinal direction instead of a lateral direction so as to meet the demand. This developer conveyance mechanism disposed in the longitudinal direction includes a first developer conveyer disposed in a lower side thereof to collect a developer from a developer carrying member after an image is developed. This developer conveyance mechanism also includes a second developer conveyer disposed in an upper side to supply the developer to the developer carrying member. In other words, the first and second developer conveyers are functionally separated, and the related art image forming apparatus has increased an agitation capability with respect to the developer. However, this related art image forming apparatus generates density unevenness and density reduction, which may be caused by insufficient agitation of the developer.
One example has attempted to modify the related art image forming apparatus by employing a related art development device shown in FIG. 1 that is capable of providing a quality image without the image unevenness.
Referring to FIG. 1, the related art development device includes a first conveyance path 227, a second conveyance path 228, and a third conveyance path 230. The first conveyance path 227, the second conveyance path 228, and the third conveyance path 230 include a surplus developer, a collected developer, and a circulating developer, respectively. The surplus developer from the first conveyance path 227 and the collected developer from the second conveyance path 228 are combined and agitated while conveying through the third conveyance path 230. The developer is combined and agitated as the circulating developer is circulated to the first conveyance path 227. This circulating developer has a relatively high toner density evenness, and the related art image forming apparatus with the related art development device may become capable of providing the quality image without the image unevenness when the image is formed with a high print density ratio. Therefore, the agitation capability with respect to the developer may be increased by having an additional developer conveyer of the third conveyance path 230 as a third developer conveyer.
Another example has attempted to employ another related art development device that includes a first auger housed in a first agitation space, a second auger housed in a second agitation space, a third auger housed in a third agitation space, a first division wall, and a first opening. The first auger supplies a developer to a developer carrying member, the second auger disposed below the first auger conveys the developer to a direction opposing to the first auger, and the third auger, disposed below the developer carrying member, conveys the developer to a direction opposing to the second auger. The first division wall separates the second and the third agitation spaces. The first opening is communicated with the second and the third agitation spaces in an end portion of the first division wall, and transfers the developer from a downstream side of a developer conveyance direction of the third auger to an upstream side of the second auger. Therefore, the developer is collected in the second agitation space after the image is developed. The developer is collected in one direction by the third auger, and is returned to the first agitation space when a toner is supplied.